U.S. patent application number 13/375848 was filed with the patent office on 2013-04-18 for method and device for determining a number of mimo layers.
The applicant listed for this patent is Dirk Gerstenberger, Daniel Larsson, Kai-Erik Sunell, Henning Wiemann. Invention is credited to Dirk Gerstenberger, Daniel Larsson, Kai-Erik Sunell, Henning Wiemann.
Application Number | 20130095816 13/375848 |
Document ID | / |
Family ID | 45063197 |
Filed Date | 2013-04-18 |
United States Patent
Application |
20130095816 |
Kind Code |
A1 |
Gerstenberger; Dirk ; et
al. |
April 18, 2013 |
METHOD AND DEVICE FOR DETERMINING A NUMBER OF MIMO LAYERS
Abstract
The embodiments herein relate to a method in a base station for
communicating with a user equipment in the communication network.
The base station is configured to communicate with the user
equipment according to a selectable of at least two user equipment
categories. Based on information about a selected user equipment
category, the base station determines a first number of maximum
transmission layers supported by the base station. The base station
communicates with the user equipment according to up to the
determined first number of maximum transmission layers and
according to the selected user equipment category.
Inventors: |
Gerstenberger; Dirk;
(Stockholm, SE) ; Sunell; Kai-Erik; (Bromma,
SE) ; Wiemann; Henning; (Aachen, DE) ;
Larsson; Daniel; (Solna, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Gerstenberger; Dirk
Sunell; Kai-Erik
Wiemann; Henning
Larsson; Daniel |
Stockholm
Bromma
Aachen
Solna |
|
SE
SE
DE
DE |
|
|
Family ID: |
45063197 |
Appl. No.: |
13/375848 |
Filed: |
October 14, 2011 |
PCT Filed: |
October 14, 2011 |
PCT NO: |
PCT/SE11/51228 |
371 Date: |
December 2, 2011 |
Current U.S.
Class: |
455/422.1 |
Current CPC
Class: |
H04W 88/10 20130101;
H04W 72/0406 20130101; H04W 72/048 20130101; H04W 88/06 20130101;
H04B 7/0413 20130101; H04W 72/042 20130101 |
Class at
Publication: |
455/422.1 |
International
Class: |
H04W 4/00 20090101
H04W004/00 |
Claims
1.-33. (canceled)
34. A method in a base station for communicating with a user
equipment in the communication network, the base station being
configured to communicate with the user equipment according to a
selectable of at least two user equipment categories, the method
comprising: based on information about a selected user equipment
category, determining a first number of maximum transmission layers
supported by the base station; and communicating with the user
equipment according to up to the determined first number of maximum
transmission layers and according to the selected user equipment
category.
35. The method according to claim 34, further comprising
transmitting information to the user equipment about the first
number of maximum transmission layers.
36. The method according to claim 34, further comprising:
receiving, from the user equipment, information about the at least
two user equipment categories and a number of maximum transmission
layers for each user equipment category.
37. The method according to claim 36, wherein the information about
the first number of maximum transmission layers is transmitted to
the user equipment when the first number of maximum transmission
layers is larger than a second number of maximum transmission
layers.
38. The method according to claim 37, further comprising: receiving
channel state information according to the first number of maximum
transmission layers from the user equipment, which channel state
information comprises information about a state of a radio channel
between the user equipment and the base station.
39. The method according to claim 34, wherein the information about
the first number of maximum transmission layers is transmitted to
the user equipment via a radio resource control, referred to as
RRC, protocol.
40. The method according to claim 34, wherein the communicating
with the user equipment according to up to the first number of
maximum transmission layers and according to the selected user
equipment category is a downlink communication in a direction from
the base station to the user equipment.
41. The method according to claim 34, wherein the selected user
equipment category and the first number of maximum transmission
layers are associated with release 8/9 of long term evolution,
referred to as LTE, and the second number of maximum transmission
layers are associated with release 10 of LTE, or wherein the
selected user equipment category and the first number of maximum
transmission layers are associated with release 10 of LTE and the
second number of maximum transmission layers are associated with
release 8/9 of LTE.
42. A method in a user equipment for communicating with a base
station in a communication network, the user equipment being
configured to communicate with the base station according to a
selectable of at least two user equipment categories, the method
comprising: based on information about a selected user equipment
category, determining a first number of maximum transmission layers
supported by the user equipment; and communicating with the base
station according to the up to the first number of maximum
transmission layers and according to the selected user equipment
category.
43. The method according to claim 42, further comprising receiving
information from the base station about the first number of maximum
transmission layers.
44. The method according to claim 42, further comprising:
transmitting, to the base station, information about the at least
two user equipment categories and a number of maximum transmission
layers for each user equipment category.
45. The method according to claim 44, wherein the information about
the first number of maximum transmission layers is received from
the base station when the first number of transmission layers is
larger than a second number of maximum transmission layers.
46. The method according to claim 42, further comprising: obtaining
information about a state of a radio channel between the user
equipment and the base station and according to the first number of
maximum transmission layers; transmitting the channel state
information to the base station.
47. The method according to claim 42, wherein information about the
first number of maximum transmission layers is received from the
base station via a radio resource control, referred to as RRC,
protocol.
48. The method according to claim 42, wherein the communicating
with the base station according to up to the first number of
maximum transmission layers and according to the selected user
equipment category is a downlink communication in a direction from
the base station to the user equipment.
49. The method according to claim 42, wherein the information about
the first number of maximum transmission layers is preconfigured in
the user equipment.
50. The method according to claim 42, wherein the selected user
equipment category and the first number of maximum transmission
layers are associated with release 8/9 of long term evolution,
referred to as LTE, and the second number of maximum transmission
layers are associated with release 10 of LTE, or wherein the
selected user equipment category and the first number of maximum
transmission layers are associated with release 10 of LTE and the
second number of maximum transmission layers are associated with
release 8/9 of LTE.
51. A base station for communicating with a user equipment in the
communication network, the base station being configured to
communicate with the user equipment according to a selectable of at
least two user equipment categories, the base station comprising: a
determining unit configured to, based on information about a
selected user equipment category, determine a first number of
maximum transmission layers supported by the base station; and a
communicating unit configured to communicate with the user
equipment according to up to the first number of maximum
transmission layers and according to the selected user equipment
category.
52. The base station according to claim 51, further comprising a
transmitting port configured to transmit information to the user
equipment about the first number of maximum transmission
layers.
53. The base station according to claim 51, further comprising: a
receiving port configured to receive, from the user equipment,
information about the at least two user equipment categories and a
number of maximum transmission layers for each user equipment
category.
54. The base station according to claim 53, wherein the information
about the first number of maximum transmission layers is
transmitted to the user equipment when the first number of maximum
transmission layers is larger than a second number of maximum
transmission layers.
55. The base station according to claim 51, wherein the receiving
port is further configured to receive channel state information
according to the first number of maximum transmission layers from
the user equipment, which channel state information comprises
information about a state of a radio channel between the user
equipment and the base station.
56. The base station according to claim 51, wherein the
transmitting port is further configured to transmit the information
about the first number of maximum transmission layers to the user
equipment via a radio resource control, referred to as RRC,
protocol.
57. The base station according to claim 51, wherein the
communication with the user equipment according to up to the first
number of maximum transmission layers and according to the selected
user equipment category is a downlink communication in a direction
from the base station to the user equipment.
58. The base station according to claim 51, wherein the selected
user equipment category and the first number of maximum
transmission layers are associated with release 8/9 of long term
evolution, referred to as LTE, and the second number of maximum
transmission layers are associated with release 10 of LTE, or
wherein the selected user equipment category and the first number
of maximum transmission layers are associated with release 10 of
LTE and the second number of maximum transmission layers are
associated with release 8/9 of LTE.
59. A user equipment for communicating with a base station in a
communication network, the user equipment being configured to
communicate with the base station according to a selectable of at
least two user equipment categories, the user equipment comprising:
a determining unit configured to, based on information about a
selected user equipment category, determine a first number of
maximum transmission layers supported by the user equipment; and a
communicating unit configured to communicate with the base station
according to up to the first number of maximum transmission layers
and according to the selected user equipment category.
60. The user equipment according to claim 59, further comprising a
receiving port configured to receive information from the base
station about the first number of maximum transmission layers.
61. The user equipment according to claim 59, further comprising: a
transmitting port configured to transmit, to the base station,
information about the at least two user equipment categories and a
number of maximum transmission layers for each user equipment
category.
62. The user equipment according to claim 61, wherein the receiving
port is further configured to receive the information about the
first number of maximum transmission layers from the base station
when the first number of transmission layers is larger than a
second number of maximum transmission layers.
63. The user equipment according to claim 59, further comprising:
an obtaining unit configured to obtain information about a state of
a radio channel between the user equipment and the base station and
according to the first number of maximum transmission layers; and a
transmitting port configured to transmit the channel state
information to the base station.
64. The user equipment according to claim 59, wherein information
about the first number of maximum transmission layers is received
from the base station via a radio resource control, referred to as
RRC, protocol.
65. The user equipment according to claim 59, wherein the
communicating with the base station according to up to the first
number of maximum transmission layers and according to the selected
user equipment category is a downlink communication in a direction
from the base station to the user equipment.
66. The user equipment according to claim 59, wherein the
information about the first number of maximum transmission layers
is preconfigured in the user equipment.
67. The user equipment according to claim 59, wherein the selected
user equipment category and the first number of maximum
transmission layers are associated with release 8/9 of long term
evolution, referred to as LTE, and the second number of maximum
transmission layers are associated with release 10 of LTE, or
wherein the selected user equipment category and the first number
of maximum transmission layers are associated with release 10 of
LTE and the second number of maximum transmission layers are
associated with release 8/9 of LTE.
Description
TECHNICAL FIELD
[0001] Embodiments herein relate generally to a base station and a
method in the base station, and to a User Equipment (UE) and a
method in the user equipment. More particularly the embodiments
herein relate to radio communications, and in particular, to user
equipment capabilities.
BACKGROUND
[0002] In a typical cellular radio system, wireless terminals
communicate via a Radio Access is Network (RAN) to one or more Core
Networks (CN). The wireless terminals are also known as mobile
stations and/or user equipment units, such as mobile telephones,
smart phones, cellular telephones, tablet computers and laptops
with wireless capability, e.g., mobile termination, and thus may
be, for example, portable, pocket-storable, hand-held,
computer-comprised, or vehicle-mounted mobile devices which
communicate voice and/or data via the radio access network. In the
following, the term user equipment is used when referring to the
wireless terminal.
[0003] The RAN covers a geographical area which is divided into
cell areas, with each cell area being served by a Base Station
(BS), e.g., a Radio Base Station (RBS), which in some networks is
also called NodeB, B node, evolved Node B (eNB) or Base Transceiver
Station (BTS). The term base station will be used in the following
when referring to any of the above examples. A cell is a
geographical area where radio coverage is provided by the radio
base station equipment at a base station site. The base stations
communicate over the air interface operating on radio frequencies
with the user equipment units within range of the base
stations.
[0004] In some versions, particularly earlier versions, of the
radio access network, several base stations are typically
connected, e.g., by landlines or microwave, to a Radio Network
Controller (RNC). The radio network controller, also sometimes
termed a Base Station Controller (BSC), supervises and coordinates
various activities of the base station(s) connected thereto. The
radio network controllers are typically connected to one or more
core networks.
[0005] The Universal Mobile Telecommunications System (UMTS) is a
third generation mobile communication system, which evolved from
the Global System for Mobile Communications (GSM), and is intended
to provide improved mobile communication services based on Wideband
Code Division Multiple Access (WCDMA) access technology. Universal
Terrestrial Radio Access Network (UTRAN) is essentially a radio
access network using wideband code division multiple access for
user equipment units. The Third Generation Partnership Project
(3GPP) has undertaken to further evolve the UTRAN and GSM based
radio access network technologies.
[0006] Long Term Evolution (LTE) is a variant of a 3GPP radio
access technology wherein the radio base station nodes are
connected directly to a core network, rather than to radio network
controller nodes. In LTE the functions of a radio network
controller node are generally performed by the radio base station
nodes. As such, the radio access network of an LTE system has an
essentially "flat" architecture comprising radio base station nodes
without reporting to radio network controller nodes. LTE was
introduced in 3GPP with release 8. Release 9 and release 10 are
later releases of LTE. For example, release 8 may be referred to as
e.g. rel-8, release 8, LTE release 8 or 3GPP release 8. The terms
"codeword," "layer," "precoding," and "beam forming" have been
adapted specifically for LTE to refer to signals and their
processing. A codeword represents user data before it is formatted
for transmission. The term "layer" is synonymous with stream. For
Multiple Input Multiple Output (MIMO), at least two layers must be
used. Up to four are allowed. The number of layers is always less
than or equal to the number of antennas. Precoding modifies the
layer signals before transmission. This may be done for diversity,
beam steering, or spatial multiplexing. Beam forming modifies the
transmit signals to give the best Carrier to
Interference-plus-Noise Ratio (CINR) at the output of the
channel.
[0007] In LTE, Hybrid Automatic Repeat reQuest (HARQ) with
incremental redundancy is used. HARQ is a technique that enables
faster recovery from errors in communication networks by storing
corrupted packets in the receiving device rather than discarding
them. Even if retransmitted packets have errors, a good packet may
be derived from the combination of bad ones. Instead of
re-transmitting the same portion of the codeword, different
redundancy versions are re-transmitted yielding an extra gain over
Chase combining.
[0008] Ideally, a full buffer is available at the receiver side
such that the received soft values for an entire codeword may be
stored. However, due to the user equipment complexity and cost
concerns, the soft buffer size in a user equipment is limited. For
higher rate transmissions, where larger codewords are sent from the
transmitter, the user equipment has limited buffer space and is not
able to store the complete codeword. The base station may transmit
coded bits the user equipment is not able to store, or worse, the
user equipment does not know that these are other bits and confuses
them with bits it previously has stored.
[0009] FIG. 1 depicts simplified a complete codeword and also how
many soft bits the user equipment is able to store. FIG. 1
illustrates an encoded transport block and coded bits stored by the
user equipment, i.e. soft buffer size. As seen in FIG. 1, the
complete codeword comprises systematic bits and parity buts, and
the soft buffer size comprises all systematic bits and some of the
parity bits of the complete codeword. A parity bit is a bit that is
added to a group of source bits to ensure that the number of set
bits in the outcome is even or odd. The parity bit may be used to
detect single or any other odd number of errors in an output. If
the base station and the user equipment have the same understanding
about the soft buffer size, then the base station will not transmit
coded bits which the user equipment is not able to store. Instead,
it only takes those coded bits stored by the user equipment and
uses those bits for (re)transmissions. This is depicted by the
circular buffer shown in FIG. 2. The term circular buffer refers to
an area in a memory which is used to store incoming data. When the
buffer is filled, new data is written starting at the beginning of
the buffer and overwriting the old data. The codeword, i.e. the
systematic bits and the parity bits, are stored in the circular
buffer. FIG. 2 illustrates bits used in a first transmission and
re-transmissions, derived from the circular buffer. The size of the
circular buffer matches the soft buffer size of the user equipment.
The complete circle in FIG. 2 corresponds to the soft buffer size
and not to the entire codeword. In the first transmission,
depending on the code rate, some or all systematic bits, and none
or some parity bits are transmitted. In a retransmission the
starting position is changed and bits corresponding to another part
of the circumference, e.g. another point in the circular buffer,
are transmitted.
[0010] In LTE release 8 using Frequency-Division Duplexing (FDD),
each user equipment has up to 8 HARQ processes per component
carrier. Each HARQ process may comprise up to two sub-processes for
supporting dual-codeword MIMO transmissions. Release 8 of LTE
divides the available soft buffer equally into the configured
number of HARQ processes. Each of the divided soft buffers may be
used to store soft values of the received codewords. In case of
dual-codeword MIMO transmission, the divided soft buffer is further
divided equally to store the soft values of the two received
codewords.
[0011] In 3GPP the soft buffer size allocation is provisioned as
below:
[0012] The circular buffer w.sub.k for the r-th coded block is
generated as follows:
w.sub.k=v.sub.k.sup.(0) for k=0, . . . , K.sub..PI.-1
w.sub.K.sub..PI..sub.+2k=v.sub.k.sup.(1) for k=0, . . . ,
K.sub..PI.-1
w.sub.K.sub..PI..sub.+2k+1=v.sub.k.sup.(2) for k=0, . . . ,
K.sub..PI.-1
where K.sub..PI. is a constant.
[0013] The circular buffer has the length K.sub.w=3K.sub..PI..
[0014] Denote the soft buffer size for the transport block by
N.sub.IR bits and the soft buffer size for the r-th code block by
N.sub.cb bits. The size N.sub.cb is obtained as follows, where C is
the number of code blocks:
N cb = min ( N IR C , K w ) for downlink turbo coded transport
channels ##EQU00001##
[0015] N.sub.cb=K.sub.w for uplink turbo coded transport
channels,
[0016] where N.sub.IR is equal to:
N IR = N soft K MIMO min ( M DL_HARQ , M limit ) ##EQU00002##
[0017] where:
[0018] N.sub.soft is the total number of soft channel bit.
[0019] K.sub.MIMO is equal to 2 if the user equipment is configured
to receive Physical Downlink Shared Channel (PDSCH) transmissions
based on transmission modes 3, 4 or 8, 1 otherwise.
[0020] M.sub.DL.sub.--.sub.HARQ is the maximum number of DL HARQ
processes.
[0021] M.sub.limit is a constant equal to 8.
[0022] The Soft Buffer (SB) allocation for the single-codeword
transmission modes is illustrated in FIG. 3. FIG. 3 illustrates 8
allocated soft buffers, where SB0 illustrates a first soft buffer
for a first codeword, SB1 illustrates a second soft buffer for a
second codeword, SB2 illustrates a third soft buffer for a third
codeword etc. FIG. 3 shows soft buffer allocation in LTE release 8
when the Physical Downlink Shared Channel (PDSCH) transmission mode
is other than mode 3, 4 or 8. It may be observed that there is a
buffer reserved for each codeword.
[0023] The soft buffer allocation for the dual-codeword
transmission modes is illustrated in FIG. 4. FIG. 4 illustrates 16
allocated soft buffers, where SB0a illustrates a first buffer for a
first codeword, SB0b illustrates a second buffer for a second
codeword, SB1a illustrates a third buffer for a third codeword,
SB1b illustrates a fourth soft buffer for a fourth codeword etc.
The soft buffer applies to a codeword. The codeword is a term used
for the coded bits associated with a transport block. FIG. 4 shows
soft buffer allocation in release 8 of LTE when the PDSCH
transmission mode is mode 3, 4 or 8. The transmission modes will be
described in more detail below.
[0024] The buffer reserved for each codeword is only half of the
previous operating case. The soft buffer limitation problem is
particularly acute in dual-codeword MIMO transmission operations.
This limitation reduces the effectiveness of soft combining gains
from incremental redundancy retransmissions.
[0025] Carrier Aggregation.
[0026] The release 8 of LTE supports bandwidths up to 20 Mega Hertz
(MHz). However, in order to meet the International Mobile
Telecommunications-Advanced (IMT-Advanced) requirements, 3GPP
initiated work on LTE release 10. One part of LTE release 10 is to
support bandwidths larger than 20 MHz. An important requirement for
LTE release 10 is to assure backward compatibility with LTE release
8, including spectrum compatibility. As a result, a carrier of LTE
release 10, which is wider than 20 MHz, may appear as a number of
smaller LIE carriers to a user equipment of LTE release 8. Each
such carrier may be referred to as a component carrier or cells.
For early LTE release 10 deployments, it may be expected that there
will be a smaller number of LTE release 10-capable user equipments
compared to many LTE legacy user equipments. Therefore, it is
desirable to assure an efficient use of a wide carrier by legacy
user equipments, which means that it may be possible to implement
carriers where legacy user equipments may be scheduled in all parts
of the wideband LTE release 10 carrier. One way to achieve this
would be using Carrier Aggregation (CA).
[0027] Carrier aggregation implies that a user equipment supporting
LTE release 10 may receive multiple component carriers, where the
component carriers have, or at least may have, the same structure
as a carrier of LIE release 8. Carrier Aggregation is illustrated
in is FIG. 5. The x-axis of FIG. 5 denotes the width of the
spectrum used for the five component carriers and the y-axis
defines the energy per frequency unit.
[0028] Soft Buffer Operation in Carrier Aggregation.
[0029] In LTE each component carrier operates with its own set of
HARQ processes. Since the total soft buffer memory needs to be
shared among component carriers, the soft buffer size per component
carrier may vary depending on the number of configured component
carriers and the number of configured MIMO transmission modes for
each component carriers. The available soft buffer size for each
codeword also depends on how the soft buffer is divided and
allocated amongst all codewords.
[0030] Multi-Antenna Support in LTE.
[0031] Multi-antenna capabilities are included already in release 8
of LTE, and are important enablers for high data rates, improved
coverage and capacity. The multiple antennas at transmitters and
receivers may be used in different ways. Diversity techniques are
used to improve the robustness of the link. Beam-forming techniques
may be used to improve the coverage. Spatial multiplexing provides
a means to enhance the spectral efficiency of the link and improves
the performance of the whole system if properly designed. Peak
rates may be substantially increased using spatial multiplexing and
is ideally be increased proportionally to the minimum number of
transmit and receive antennas of the link, provided that the
Signal-to-Noise Ratio (SNR) is high enough and that the channel
conditions are beneficial. Realistic gains are highly channel
dependent, they require a high SNR and beneficial interference
situations of the relevant link, but may be substantially improved
provided that the SNR is sufficiently high. Examples are low system
load scenarios or when the user equipment is close to the cell
center.
[0032] The downlink in LTE release 8 supports Single-User MIMO
(SU-MIMO) spatial multiplexing of up to four layers via codebook
based precoding. In addition, transmit diversity modes as well as
beamforming with single-layer transmission are supported in the
downlink of LTE release 8. In LTE release 9, an enhanced downlink
transmission mode is introduced in which the beamforming
functionality is extended to also support dual-layer transmission,
and in which Multi-User MIMO (MU-MIMO) operation is offered where
different layers are transmitted to different users. The uplink
multi-antenna support in LTE release 8/9 is limited to user
equipment antenna selection, which is optional in all UE
categories. The UE categories will be described in more detail
below.
[0033] A user equipment of LTE release 8 assumes its number of
layers based on the minimum of what the base station supports and
what the user equipment supports. The user equipment determines how
many layers the base station supports by either blindly detecting
how many Cell-specific Reference Signal (CRS) antenna ports the
base station is transmitting from, or in the case of a HandOver
(HO), by receiving the information about the how many antenna ports
the target cells supports in the HO-command.
[0034] Multi-antenna transmission is an important feature in LTE
release 8. LTE supports the following 8 transmission modes (TM):
[0035] Mode 1: Single antenna port. [0036] Mode 2: Transmit
diversity. [0037] Mode 3: Open-loop spatial multiplexing. [0038]
Mode 4: Closed-loop spatial multiplexing. [0039] Mode 5: MU-MIMO.
[0040] Mode 6: Closed-loop spatial multiplexing, single layer.
[0041] Mode 7: Single antenna port, user equipment specific
reference signal. [0042] Mode 8: Single or dual-layer transmission
with user equipment specific reference signal.
[0043] LTE-Advanced, i.e. LTE release 10, comprises a mode 9, in
addition to modes 1-8. Mode 9 is a multilayer transmission mode
supporting closed-loop SU-MIMO up to rank 8 and enhanced MU-MIMO
support.
[0044] UE Category Signaling.
[0045] User equipments may be categorized in different user
equipment categories, called UE categories or UE classes, which
defines the overall performance and capabilities of the user
equipment. The user equipment category is from now on referred to
as UE category. The UE categories are needed to ensure that the
base station may communicate correctly with the user equipment. By
letting the base station know the UE category, it is able to
determine the performance of the user equipment and communicate
with it accordingly.
[0046] As the UE category defines the overall performance and the
capabilities of the user equipment, it is possible for the base
station to communicate using capabilities that it knows the user
equipment possesses. Accordingly, the base station will not
communicate beyond the performance of the user equipment. Different
values of a buffer size are associated with each UE category.
[0047] In LTE release 8/9, there are five UE categories, 1-5. LTE
release 10 has three additional categories, 6-8.
[0048] The definition of UE categories of LTE release 10 builds
upon the principles used in LTE release 8/9, where the number of UE
categories is limited to avoid fragmentation of user equipment
implementation variants in the market. The LTE release 10 UE
categories are defined in terms of peak rate, ranging from 10, 50,
100, 150 and 300 Mbps up to about 3 Gbps in the downlink. Different
realizations of the peak rates are possible within a UE category.
For example, in categories 6 and 7, it is possible to either
support two layers of MIMO together with carrier aggregation of 40
MHz, or four layers of MIMO with a single carrier of 20 MHz. Both
configurations support up to 300 Mbps. The LTE release 8/9 UE
categories are reused, supporting, e.g. aggregation of two
component carriers with up to 10 MHz bandwidth each for a user
equipment of category 3. It is expected that additional UE
categories may be defined in the future. LTE release 10 supports a
high-end UE category combining aggregation of five component
carriers of 20 MHz each with eight layer MIMO, which supports a
total peak data rate of about 3 Gbps for LTE-Advanced. Table 1
below shows UE categories supported in LTE release 10. The left
most column comprises the UE categories 1-8. The next column
comprises the maximum number of DownLink-Shared CHannel (DL-SCH)
transport block bits received within a Transmission Time Interval
(TTI). The middle column comprises the maximum number of bits of a
DL-SCH transport block received within a TTI. The column to the
right of the middle column comprises the total number of soft
channel bits. The right most column comprises the maximum number of
supported layers for spatial multiplexing in DL. Spatial
multiplexing is a transmission technique in MIMO wireless
communication to transmit independent and separately encoded data
signals from each of the multiple transmit antennas.
TABLE-US-00001 TABLE 1 UE categories supported in LTE release 10
Maximum number of Maximum number of Maximum number of DL-SCH
transport bits of a DL-SCH Total number supported layers UE block
bits received transport block of soft for spatial Category within a
TTI received within a TTI channel bits multiplexing in DL 1 10296
10296 250368 1 2 51024 51024 1237248 2 3 102048 75376 1237248 2 4
150752 75376 1827072 2 5 299552 149776 3667200 4 6 301504 149776 (4
layers) 3667200 2 or 4 75376 (2 layers) 7 301504 149776 (4 layers)
3667200 2 or 4 75376 (2 layers) 8 2998560 299856 35982720 8
[0049] The user equipment capability signaling of UE categories is
defined in the following way. LTE release 8/9 categories 1-5 are
signaled from the user equipment to the base station via the Radio
Resource Control (RRC) protocol. The RRC protocol handles the
control plane signaling of Layer 3 between the user equipment and
the UTRAN. LTE release 10 categories are signaled from the user
equipment to the base station in separately via the RRC protocol,
using a LTE release 10 part of the RRC protocol. The receiver of
the message is the base station, and it also the base station that
uses the received information. However, the user equipment is not
aware of the release of the base station. So in order to be able to
operate in a legacy network, a LTE release 10 user equipment would
thus report both a LTE release 8/9 UE category (1-5) using a LTE
release 8/9 part of the RRC protocol and a LTE release 10 UE
category (6-8) using a LTE release 10 part of the RRC protocol. The
LTE release 10 UE category would be understood by a LTE release 10
base station, but not by the LTE release 8/9 base station. In
addition, a LTE release 10 user equipment also informs the base
station per frequency band combination about the supported number
of supported MIMO layers in UpLink (UL) and DownLink (DL), as well
as the number of supported aggregated component carriers. This
information is only understood by a LTE release 10 base
station.
[0050] As an example, a LTE release 10 user equipment, e.g.,
category 6, indicates to a LTE release 10 base station that it
supports up 4 MIMO layers in the DownLink (DL). The LTE release 10
user equipment may provide this MIMO layer information in an
Information Element (IE) sent in addition to the category values.
This information element is understood by a LTE release 10 base
station but ignored by a LTE release 8/9 base station. A LTE
release 8 base station that supports 4 MIMO layers in DL identifies
the user equipment through its LTE release 8/9 category e.g.,
category 4, and therefore assumes that the user equipment supports
only 2 layers of DL MIMO.
[0051] Because the user equipment is not aware of the release of
the base station, it does not know whether to operate according to
an older release, e.g., the LTE release 8/9 category, e.g. category
4, or a newer release, e.g., the LTE release 10 category, e.g.
category 6. This has serious consequences as the user equipment
operates differently depending on the category. In this example,
the user equipment may assume that the base station operates
according to 4 layer MIMO in DL, as it detects the Cell Reference
Signal (CRS) pattern according to 4 layer MIMO, and sends feedback
to the base station to support 4 layer DL MIMO operation such as a
rank indicator greater than 2, Channel Quality Indicator (CQI), and
Pre-coding Matrix Index (PMI). But this leads to corrupted UpLink
(UL) control signaling as the base station assumes a maximum rank
of 2 when decoding the control signaling, according to the LTE
release 8/9 category, e.g. category 4, indicated by the user
equipment. It may also lead to corrupted UL data if the UL data is
multiplexed together with the UL control signaling.
[0052] As another example, a LTE release 10 user equipment may
support a higher number of DL MIMO layers than what is required by
the UE category. If the user equipment operates according to the
higher number of DL MIMO layers in a base station that does not
operator with this higher number of DL MIMO layers, similar
problems arise as described above.
SUMMARY
[0053] An object of embodiments herein is therefore to obviate at
least one of the above disadvantages and to provide improved
communication between a user equipment and a base station in a
communications network.
[0054] According to a first aspect, the object is achieved by a
method in a base station for communicating with a user equipment in
the communication network. The base station is configured to
communicate with the user equipment according to a selectable of at
least two user equipment categories. Based on information about a
selected user equipment category, the base station determines a
first number of maximum transmission layers supported by the base
station. The base station communicates with the user equipment
according to up to the first number of maximum transmission layers
and according to the selected user equipment category.
[0055] According to a second aspect, the object is achieved by a
method in a user equipment for communicating with a base station in
a communication network. The user equipment is configured to
communicate with the base station according to a selectable of at
least two user equipment categories. Based on information about the
selected user equipment category, the user equipment determines a
first number of maximum transmission layers supported by the user
equipment. The user equipment communicates with the base station
according to up to the first number of maximum transmission layers
and according to the selected user equipment category.
[0056] According to a third aspect, the object is achieved by a
base station for communicating with a user equipment in the
communication network. The base station is configured to
communicate with the user equipment according to a selectable of at
least two user equipment categories. The base station comprises a
determining unit which is configured to, based on information about
the selected user equipment category, determine a first number of
maximum transmission layers supported by the base station. The base
station comprises a communicating unit configured to communicate
with the user equipment according to up to the first number of
maximum transmission layers and according to the selected user
equipment category.
[0057] According to a fourth aspect, the object is achieved by a
user equipment for communicating with a base station in a
communication network. The user equipment is configured to
communicate with the base station according to a selectable of at
least two user equipment categories. The user equipment comprises a
determining unit configured to, based on information about the
selected user equipment category, determine a first number of
maximum transmission layers supported by the user equipment. The
user equipment further comprises a communicating unit which is
configured to communicate with the base station according to up to
the first number of maximum transmission layers and according to
the selected user equipment category.
[0058] Since the base station and the user equipment have same
understanding of the number of maximum supported DL MIMO layers,
improved communication between a user equipment and a base station
in a communications network is provided.
[0059] Embodiments herein afford many advantages, of which a
non-exhaustive list of examples follows:
[0060] An advantage of the embodiments herein is that they allow a
LTE release 10 user equipment to operate in a legacy network. The
embodiments herein allow a LTE release 10 user equipment with a
number of DL MIMO layers higher than the required value in the UE
category to operate in a network.
[0061] An further advantage of the embodiments herein is that the
base station and the user equipment will have the same
understanding of the number of maximum supported DL MIMO layers.
The base station may avoid scheduling the user equipment with more
DL MIMO layers then what it supports. The user equipment will not
report CSI feedback that the base station does not understand. This
has two advantages. Firstly, the base station may schedule the
correct number of DL MIMO layers in DL, so that user equipment is
only scheduled with an amount its current channel supports or what
it actually supported by its capabilities. Secondly, in case the
CSI feedback is transmitted multiplexed together with data on
PUSCH, the data on PUSCH will be possible to decode as the size of
the CSI report will be known by the base station.
[0062] Another advantage of the embodiments herein is that they
provide improved coverage and capacity in the communications
network.
[0063] A further advantage is that the embodiments herein reduce
the risk of corrupted UL control signaling.
[0064] The embodiments herein are not limited to the features and
advantages mentioned above. A person skilled in the art will
recognize additional features and advantages upon reading the
following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0065] The embodiments herein will now be further described in more
detail in the following detailed description by reference to the
appended drawings illustrating the embodiments and in which:
[0066] FIG. 1 is a schematic diagram showing an encoded transport
block and coded bits stored by a user equipment, i.e. soft buffer
size.
[0067] FIG. 2 is a schematic diagram showing that bits used in the
first transmission and re-transmissions are derived from a circular
buffer.
[0068] FIG. 3 is a schematic diagram view showing soft buffer
allocation in release 8 of LTE when the PDSCH transmission mode is
other than mode 3, 4 or 8.
[0069] FIG. 4 is a schematic diagram showing soft buffer allocation
in release 8 of LTE when the PDSCH transmission mode is mode 3, 4
or 8.
[0070] FIG. 5 is a diagrammatic view illustrating carrier
aggregation.
[0071] FIG. 6 is a schematic block diagram illustrating embodiments
of a communications network.
[0072] FIG. 7a-d are flowcharts illustrating embodiments of a
method.
[0073] FIG. 8 is a flowchart illustrating embodiments of a method
in a base station.
[0074] FIG. 9 is a flowchart illustrating embodiments of a method
in a user equipment.
[0075] FIG. 10 is a block diagram illustrating embodiments of a
base station.
[0076] FIG. 11 is a block diagram illustrating embodiment of a user
equipment.
[0077] FIG. 12 is a block diagram illustrating embodiments of base
station and a user equipment.
[0078] The foregoing and other objects, features, and advantages of
the embodiments herein will be apparent from the following more
particular description of preferred embodiments as illustrated in
the accompanying drawings in which reference characters refer to
the same parts throughout the various views. The drawings are not
necessarily to scale, and the dimensions of certain features may
have been exaggerated for the sake of clarity. Emphasis instead
being placed upon illustrating the principles of the embodiments
herein.
DETAILED DESCRIPTION
[0079] FIG. 6 depicts a communications network 600 in which
embodiments herein may be implemented. The communications network
600 may in some embodiments apply to one or more radio access
technologies such as for example LTE, LTE Advanced, WCDMA, GSM,
WiMAX, or any other 3GPP radio access technology.
[0080] The communications network 600 comprises a base station 603
serving a cell. The base station 603 may be a base station such as
a NodeB, an eNodeB, or any other network unit capable to
communicate over a radio carrier 604 with a user equipment 605
being present in the cell. The base station 603 may be a LTE
release 8/9 or a LTE release 10 base station.
[0081] The user equipment 605 may be any suitable communication
device or computational device with communication capabilities
capable to communicate with a base station over a radio channel,
for instance but not limited to mobile phone, tablet computer,
smart phone, personal digital assistant (PDA), laptop, MP3 player
or portable DVD player, or similar media content devices, digital
camera, or even stationary devices such as a PC. A PC may also be
connected via a mobile station as the end station of the
broadcasted or multicasted media. The user equipment 605 may also
be an embedded communication device in e.g. electronic photo
frames, cardiac surveillance equipment, intrusion or other
surveillance equipment, weather data monitoring systems, vehicle,
car or transport communication equipment, etc. The user equipment
605 is referred to as UE in some of the figures. The user equipment
605 may be a LTE release 8/9 or LTE release 10 user equipment.
[0082] A user equipment 605 of LTE release 8/9 is of UE categories
1-5. Another type is a user equipment 605 which is of UE category
6-8, as illustrated in Table 1 above. This may be referred to as a
LTE release 10 user equipment. In that case, the user equipment 605
always signals two UE categories to the base station 603,
independent of which LTE release the base station 603 is. For
example, a user equipment 605 of UE category 6 also signals the UE
category 5. If the base station 603 is of LTE release 8/9, the base
station 603 will only understand that the user equipment 605 is of
UE category 5, as the user equipment 605 signaling for of the UE
category 6 is done in such way that a base station 603 of an older
release does not understand it and simply discards this part of the
UE signaling.
[0083] The method for communicating in the communications network
according to some embodiments will now be described with reference
to examples shown in the combined signaling diagrams and flowcharts
depicted in FIGS. 7a-d.
[0084] FIG. 7a illustrates an example of an embodiment where the
user equipment 605 is of LTE release 8/9 and LTE release 10. The
base station 603 is of LTE release 8/9. As a default, the user
equipment 605 assumes that the number of maximum supported DL MIMO
layers is the number associated with the LTE release 8/9 UE
category. This is because the user equipment 605 does not know if
the base station 603 knows that the user equipment 605 supports
both LTE release 8/9 and LTE release 10. The LTE release 8/9 base
station 603 assumes the number of maximum supported DL MIMO layers
as per the required value from its LTE release 8/9 category. The
method comprises the following steps, which steps may as well be
carried out in another suitable order than described below.
Step 701a
[0085] The user equipment 605 signals its capability to act
according to at lest two different UE categories of different
releases, one of which relates to LTE release 8/9 and another
relating to LTE release 10 to the base station 603. In addition to
information about the UE categories, the user equipment 605 signals
information about a number of maximum supported DL MIMO layers for
each category, e.g. a first number of maximum transmission layers
and a second number of maximum transmission layers.
[0086] For example, the first UE category relating to LTE release
8/9 may be 3 and the second UE category relating to LIE release 10
may be category 8. The number of maximum supported DL MIMO layers
for category 3 is 2, and the number of maximum supported DL MIMO
layers for category 6 is 8, as seen from Table 1 above.
[0087] The user equipment 605 may be configured with UE capability
parameters with indicates number of maximum DL MIMO layers it may
support. This UE capability parameter may be an explicit parameter.
As a default, this parameter corresponds to the number of maximum
supported DL MIMO layers in the LTE release 8/9 UE category. Using
the example described in above, the LTE release 8/9 UE category is
3 and the corresponding number of maximum supported DL MIMO layers
is 2.
Step 702a
[0088] As mentioned above, the base station 603 is of LTE release
8/9 in this example, and therefore the base station 603 determines
a number of maximum supported DL MIMO layers according to its LTE
release 8/9 UE category.
[0089] The base station 603 signals one or more UE capability
parameters to the user equipment 605. The UE capability parameters
comprise the determined number of maximum supported DL MIMO layers
according to LTE release 8/9.
[0090] For example, the base station 603 may be of UE category 4,
and the corresponding DL MIMO layers is 2. Thus, the base station
603 signals a maximum of 2 supported DL MIMO layers to the user
equipment 605.
Step 703a
[0091] The user equipment 605 and the base station 603 communicate
according to the LTE release 8/9 UE category together with up to
the maximum supported DL MIMO layers for that UE category. For
example, the UE category is 5 and the maximum supported DL MIIMO
layers is 4.
[0092] FIG. 7b illustrates an example of an embodiment where the
user equipment 605 supports LTE release 8/9 and a LTE release 10.
FIG. 7b differs from the example shown in FIG. 7a in that the base
station 603 supports LTE release 10 and the figure comprises step
703b. As a default, the user equipment 605 assumes that the number
of maximum supported DL MIMO layers is the number associated the UE
category associated with LTE release 8/9. For example, if the UE
category of LTE release 8/9 is 3, then the associated maximum
supported DL MIMO layers is 2, as seen from Table 1 above.
[0093] The method comprises the following steps, which steps may as
well be carried out in another suitable order than described
below.
Step 701b
[0094] This step corresponds to step 701a in FIG. 7a.
[0095] The user equipment 605 signals its capability to act
according to at least two different UE categories of different
releases, one of which relates to LTE release 8/9 and another
relating to LTE release 10, to the base station 603. In addition to
information about the UE categories, the user equipment 605 signals
information about a number of maximum supported DL MIMO layers for
each category, e.g. a first number of maximum transmission layers
and a second number of maximum transmission layers.
[0096] For example, the first UE category relating to LTE release
8/9 is 3 and the second UE category relating to LTE release 10 is
category 6. The number of maximum supported DL MIMO layers for
category 3 is 2, and the number of maximum supported DL MIMO layers
for category 6 is 4, as seen from Table 1 above.
[0097] The user equipment 605 may be configured with UE capability
parameters with indicates the number of maximum DL MIMO layers it
may support. This UE capability parameter may be an explicit
parameter. As a default, this parameter corresponds to the number
of maximum supported DL MIMO layers in the LTE release 8/9 UE
category. Using the example described in above, the LTE release 8/9
UE category is 3 and the corresponding number of maximum supported
DL MIMO layers is 2.
Step 702b
[0098] This step corresponds to step 702a in FIG. 7a.
[0099] As mentioned above, the base station 603 supports LTE
release 10 UE. The base station 603 supporting LTE release 10 and
operates with a number of maximum DL MIMO layers larger than the
number related to the respective LTE release 8/9 UE category
indicated by the user equipment 605 in step 701b.
[0100] For example, the base station 603 may be of UE category 8,
which is associated with a number of 8 maximum DL MIMO layers. The
number of maximum DL MIMO layers for category 8 supported by the
base station 603 is larger than the number of maximum DL MIMO
layers for LTE release 10 indicated by the user equipment 605, UE
category 6, which is 4. 8>4. Then, the base station 603 signals
a DL MIMO layer indication to the user equipment 605 in order to
request the user equipment 605 to operate according to a MIMO mode
exceeding the number of MIMO layers according to the user
equipments 605 LTE release 10 UE category 6, e.g. to operate
according to up to 8 numbers of DL MIMO layers.
Step 703b
[0101] When the number of maximum DL MIMO layers for the UE
category 8 of LTE release 10 is determined to be larger than the
number of maximum DL MIMO layers for the UE category 6 of LTE
release 10, the user equipment 605 obtains and reports, to the base
station 603, rank, CQI, PMI, and Precoding Type Indicator (PTI)
according to the largest number of DL MIMO layers indicated by the
base station 603 in step 702b. The rank determines how many layers
the user equipment 605 assumes it may be scheduled on. The PTI sets
which type of PMI and CQI the user equipment 605 reports. The PMI
indicates which antenna weights the user equipment 605 assumes is
best to apply, i.e. in beamforming. The CQI relates to which code
rate the user equipment 605 is able to handle. If the user
equipment 605 assumes that it may use more layers then what the
base station 603 thinks, the user equipment 605 may report a too
high rank. In that case, the base station 603 is not able to
understand the rank and will misunderstand the information as
something else. It will neither be able to understand the PTI, CQI
and PMI as this information is based on rank the user equipment 605
has reported.
[0102] The base station 603 receives the rank, CQI, PMI and PTI and
uses the information do link adaption in the DL (not shown in FIG.
7b).
Step 704b
[0103] This step corresponds to step 703a in FIG. 7a.
[0104] The user equipment 605 and the base station 603 communicate
according to the LTE release 10 UE category and according to up to
the number of maximum supported DL MIMO layers for that LTE release
10 UE category.
[0105] FIG. 7c illustrates an example of an embodiment where the
user equipment 605 supports LTE release 8/9 and LTE release 10. The
base station 603 is of LTE release 10. The difference between FIGS.
7c and 7b is that the base station 603 operates with a number of DL
MIMO layers which is not larger than the required number from the
respective UE category, and does therefore not signal a DL MIMO
layer indication to the user equipment 605. As a default, the user
equipment 605 may assume that the number of maximum supported DL
MIMO layers is the same as the number of maximum transmission
layers from the UE category according to LTE release 8/9. For a
base station 603 of LTE release 10, the number of layers may
between 1 to 8 layers, as seen in Table 1. It is an operator choice
and a choice of the base station vendor what to build and use in
reality. 3GPP only specifies the user equipments 605 default values
and not the base stations 603. Simplified, the user equipment 605
is "stupid" and needs to be told what do. The base station 603 may
figure out things based on this.
[0106] The method comprises the following steps, which steps may as
well be carried out in another suitable order than described
below.
Step 701c
[0107] This step corresponds to step 701a in FIG. 7a and step 701b
in FIG. 7b.
[0108] The user equipment 605 signals its capability to act
according to at least two different UE categories of different
releases, one of which relates to LTE release 8/9 and another
relating to LTE release 10, to the base station 603. In addition to
information about the UE categories, the user equipment 605 signals
information about a number of maximum supported DL MIMO layers for
each category, e.g. a first number of maximum transmission layers
and a second number of maximum transmission layers.
[0109] For example, the first UE category relating to LTE release
8/9 may be 3 and the second UE category relating to LTE release 10
may be category 8. The number of maximum supported DL MIMO layers
for category 3 is 2, and the number of maximum supported DL MIMO
layers for category 6 is 8, as seen from Table 1 above.
[0110] The base station 603 operates with a number of DL MIMO
layers which is 4 in this example, i.e. UE category 6, which is not
larger than the required number from the respective UE category,
i.e. 8, and does therefore not signal a DL MIMO layer indication to
the user equipment 605.
Step 702c
[0111] This step corresponds to step 703a in FIG. 7a and step 704b
in FIG. 7b.
[0112] The user equipment 605 and the base station 603 communicate
using the UE category of LTE release 10 together with up to the
number of maximum supported DL MIMO layers for that LTE release 8/9
UE category.
[0113] FIG. 7d illustrates an example of an embodiment where the
user equipment 605 supports LTE release 8/9 and LTE release 10. The
base station 603 supports of LTE release 10, and operates with a
number of DL MIMO layers which is not larger than the number
associated with the respective UE category. The difference between
FIGS. 7d and 7c, is that in the example illustrated in FIG. 7d, the
base station 605 signals the DL MIMO layer indication to the user
equipment 605 even though the number of DL MIMO layers are lower
than the required number from the respective UE category. The
indication comprises information about the number of maximum DL
MIMO layers used in the base station 603. As a default, the user
equipment 605 assumes that the number of maximum supported DL MIMO
layers is the required value from the LTE release 8/9 UE
category.
[0114] The method comprises the following steps, which steps may as
well be carried out in another suitable order than described
below.
Step 701d
[0115] This step corresponds to step 701a in FIG. 7a, step 701b in
FIG. 7b and step 701c in FIG. 7c.
[0116] The user equipment 605 signals its capability to act
according to at least two different UE categories of different
releases, one of which relates to LTE release 8/9 and another
relating to LTE release 10, to the base station 603. In addition to
information about the UE categories, the user equipment 605 signals
information about a number of maximum supported DL MIMO layers for
each UE category.
[0117] For example, the first UE category relating to LTE release
8/9 may be 3 and the second UE category relating to LTE release 10
may be category 8. The number of maximum supported DL MIMO layers
for category 3 is 2, and the number of maximum supported DL MIMO
layers for category 6 is 8, as seen from Table 1 above.
Step 702d
[0118] The base station 603 operates with a number of DL MIMO
layers which is 4 in this example, i.e. UE category 6, which is not
larger than the required number from the respective UE category,
i.e. 8. Even though the number of DL MIMO layers is lower, the base
station 603 signals the number of DL MIMO layers that is used in
the base station 603, i.e. the number of DL MIMO layers which is
lower than the required number from the respective UE category.
Step 703d
[0119] This step corresponds to step 703b in FIG. 7b.
[0120] When the number of DL MIMO layers is lower than the required
number, the user equipment 605 obtains and reports, to the base
station 603, the rank, CQI, and PMI according to the number of DL
MIMO layers indicated by the base station 603 or according to the
required number from the UE category.
Step 704d
[0121] This step corresponds to step 703a in FIG. 7a, step 704b in
FIG. 7b and step 702c in FIG. 7c.
[0122] The user equipment 605 and the base station 603 communicate
using the UE category of LTE release 10 together with the number of
maximum supported DL MIMO layers for that UE category.
[0123] The signaling and restriction of the number of maximum
supported DL MIMO layers indication may be implemented in any
suitable way. In one embodiment, implicit signaling is used by the
base station 603 to the user equipment 605. For example, the
indication to the user equipment 605 of which UE category the user
equipment 605 has capability to act according to, may either be
specifically signaled to the user equipment 605 or broadcasted. In
another embodiment, the user equipment 605 assumes a certain
default value on its code book subset restriction which corresponds
to the number of maximum supported DL MIMO layers in the LTE
release 8/9 UE category that the user equipment 605 indicates. The
code book subset restriction would restrict the maximum report rank
from the user equipment 605 so that it as a default corresponds to
the number of maximum DL MIMO layers that its LTE release 8/9 UE
category supports. A LTE release 10 base station 603 has the
possibility to remove these restrictions if it wants to operate the
user equipment 605 according to the number of maximum supported DL
MIMO layers of LTE release 10. This achieves a higher throughput to
the user equipment 605.
[0124] The user equipment 605 may be configured with an explicit
parameter indicating the number of maximum DL MIMO layers it is
able to support. As a default, this parameter could correspond in
the non-limiting example to the number of maximum supported DL MIMO
layers in the LTE release 8/9 UE category that the user equipment
605 indicates. A LTE release 10 base station 605 has the
possibility to configure a different value for this parameter, if
it wants to operate the user equipment 605 according to the user
equipments 605 number of maximum supported DL MIMO layers of LTE
release 10. This achieves a higher throughput to the user equipment
605.
[0125] The method described above will now be described seen from
the perspective of the base station 603. FIG. 8 is a flowchart
describing the present method in the base station 603 for
communicating with the user equipment 605 in the communication
network 600. The base station 603 is configured to communicate with
the user equipment 605 according to a selectable of at least two
user equipment categories. The method comprises the following
steps, which steps may as well be carried out in another suitable
order than described below.
Step 801
[0126] This step corresponds to step 701a in FIG. 7a, step 701b in
FIG. 7b, step 701c in FIG. 7c and step 701d in FIG. 7d.
[0127] In some embodiments, the base station 603 receives
information about the at least two user equipment categories and a
number of maximum transmission layers for each user equipment
category. The at least two categories may be a first user equipment
category and a second user equipment category. The number of
maximum transmission layers may be a first number of maximum
transmission layers and a second number of maximum transmission
layers.
[0128] In some embodiments, the selected user equipment category
and the first number of maximum transmission layers are associated
with release 8/9 of long term evolution, referred to as LTE, and
the second number of maximum transmission layers are associated
with release 10 of LTE. In some embodiments, the selected user
equipment category and the first number of maximum transmission
layers are associated with release 10 of LTE, and the second number
of maximum transmission layers are associated with release 8/9 of
LTE.
Step 802
[0129] This step corresponds to step 702a in FIG. 7a, step 702b in
FIG. 7b, step 702c in FIG. 7c and step 702d in FIG. 7d.
[0130] Based on information about a selected user equipment
category, the base station 603 determines a first number of maximum
transmission layers supported by the base station 603.
Step 803
[0131] This step corresponds to step 703b in FIG. 7b and step 703d
in FIG. 7d.
[0132] In some embodiments, the base station 603 receives channel
state information according to the first number of maximum
transmission layers from the user equipment 605. The channel state
information comprises information about a state of a radio channel
604 between the user equipment 605 and the base station 603. The
channel state information may be rank, CQI, PMI and PTI.
Step 804
[0133] This step corresponds to step 702a in FIG. 7a, step 702b in
FIG. 7b and step 702d in FIG. 7d.
[0134] In some embodiments, the base station 603 transmits
information about the first number of maximum transmission layers
to the user equipment 605. The first number of maximum transmission
layers is supported by the base station 603.
[0135] In some embodiments, the first number of maximum
transmission layers is transmitted to to the user equipment 605
when the first number of maximum transmission layers is larger than
the second number of maximum transmission layers.
[0136] The base station 603 may transmit the information about the
first number of maximum transmission layers to the user equipment
605 via a radio resource control, referred to as RRC, protocol.
Step 805
[0137] This step corresponds to step 703a in FIG. 7a, step 704b in
FIG. 7b, step 702c in FIG. 7c and step 704d in FIG. 7d.
[0138] The base station communicates with the user equipment 605
according to up to the first number of maximum transmission layers
and according to the selected user equipment category.
[0139] In some embodiments, the communication with the user
equipment 605 using up to the first number of maximum transmission
layers and the selected user equipment category is a downlink
communication in a direction from the base station 603 to the user
equipment 605. This may be referred to as DL MIMO
communication.
[0140] The method described above will now be described seen from
the perspective of the user equipment 605. FIG. 9 is a flowchart
describing the present method in the user equipment 605 for
communicating with the base station 603 in the communication
network 600. The user equipment 605 is configured to communicate
with the base station 603 according to a selectable of at least two
user equipment categories. The method comprises the following
steps, which steps may as well be carried out in another suitable
order than described below.
Step 901
[0141] This step corresponds to step 701a in FIG. 7a, step 701c in
FIG. 7c and step 701d in FIG. 7d.
[0142] In some embodiments, the user equipment 605 transmits, to
the base station 603, information about the at least two user
equipment categories and a number of maximum transmission layers
for each user equipment category.
[0143] In some embodiments, the information about the first number
of maximum transmission layers is preconfigured in the user
equipment 605.
[0144] In some embodiments, the selected user equipment category
and the first number of maximum transmission layers are associated
with release 8/9 of long term evolution, referred to as LTE, and
the second number of maximum transmission layers are associated
with release 10 of LTE. In some embodiments, the selected user
equipment category and the first number of maximum transmission
layers are associated with release 10 of LTE and the second number
of maximum transmission layers is associated with release 8/9 of
LTE.
Step 902
[0145] This step corresponds to step 702a in FIG. 7a, step 702b in
FIG. 7b, step 702c in FIG. 7c and step 702d in FIG. 7d.
[0146] Based on information about the selected user equipment
category, the user equipment 605 determines the first number of
maximum transmission layers supported by the user equipment
605.
Step 903
[0147] This step corresponds to step 703b in FIG. 7b and step 703d
in FIG. 7d.
[0148] In some embodiments, the user equipment 605 obtains
information about a state of a radio channel 604 between the user
equipment 605 and the base station 603 and according to the first
number of maximum transmission layers.
Step 904
[0149] This step corresponds to step 703b in FIG. 7b and to step
703d in FIG. 7d.
[0150] In some embodiments, the user equipment 605 transmits the
obtained channel state information to the base station 603.
Step 905
[0151] This step corresponds to step 702a in FIG. 7a, step 702b in
FIG. 7b and step 702d in FIG. 7d.
[0152] In some embodiments, the user equipment 605 receives
information from the base station 603 about the first number of
maximum transmission layers.
[0153] In some embodiments, the user equipment 605 receives
information about the first number of maximum transmission layers
when the first number of transmission layers is larger than the
second number of maximum transmission layers.
[0154] In some embodiments, the information about the first number
of maximum transmission layers is received 906 from the base
station 603 via a radio resource control, referred to as RRC,
protocol.
Step 906
[0155] This step corresponds to step 703a in FIG. 7a, step 704b in
FIG. 7b, step 702c in FIG. 7c and to step 704d in FIG. 7d.
[0156] The user equipment 605 communicates with the base station
603 according to up to the first number of maximum transmission
layers and according to the selected user equipment category.
[0157] In some embodiments, the communicating with the base station
603 using up to the first number of maximum transmission layers and
the selected user equipment category is a downlink communication in
a direction from the base station 603 to the user equipment
605.
[0158] To perform the method steps shown in FIG. 8 for
communicating with a user equipment 605 in a communications network
600 the base station 603 comprises an arrangement as shown in FIG.
10. The base station 603 is configured to communicate with the user
equipment 605 according to a selectable of at least two user
equipment categories.
[0159] The base station 603 comprises a determining unit 1001
configured to, based on information about the selected user
equipment category, determine a first number of maximum
transmission layers supported by the base station 603.
[0160] In some embodiments, the base station 603 comprises a
transmitting port 1003 which is configured to transmit information
to the user equipment 605 about the first number of maximum
transmission layers. In some embodiments, the information about the
determined selected number of maximum transmission layers is
transmitted to the user equipment 605 when the first number of
maximum transmission layers is larger than the second number of
maximum transmission layers. In some embodiments, the transmitting
port 1003 is further configured to transmit the information about
the first number of maximum transmission layers to the user
equipment 605 via a radio resource control, referred to as RRC,
protocol. In some embodiments, the selected user equipment category
and the first number of maximum transmission layers are associated
with one of release 8/9 of long term evolution, referred to as LTE,
and the second number of maximum transmission layers is associated
with release 10 of LTE. In some embodiments, the selected user
equipment category and first number of maximum transmission layers
are associated with one of release 10 of LTE the second number of
maximum transmission layers is associated with release 8/9 of
LTE.
[0161] The base station 603 comprises a communicating unit 1005
configured to communicate with the user equipment 605 according to
up to the first number of maximum transmission layers and according
to the selected user equipment category. In some embodiments, the
communication with the user equipment 605 according to up to the
first number of maximum transmission layers and the selected user
equipment category is a downlink communication in a direction from
the base station 603 to the user equipment 605.
[0162] In some embodiments, the base station 603 comprises a
receiving port 1008 configured to receive, from the user equipment
605, information about the at least two user equipment categories
and a number of maximum transmission layers for each user equipment
category. In some embodiments, the receiving port 1008 is further
configured to receive channel state information according to the
first number of maximum transmission layers from the user equipment
605. The channel state information comprises information about a
state of a radio channel 604 between the user equipment 605 and the
base station 603.
[0163] To perform the method steps shown in FIG. 9 for
communicating with a base station 603 in a communications network
600 the user equipment 605 comprises an arrangement as shown in
FIG. 11. The user equipment 605 is configured to communicate with
the base station 603 according to a selectable of at least two user
equipment categories.
[0164] In some embodiments, the user equipment 605 comprises a
receiving port 1101 configured to receive information from the base
station 605 about the first number of maximum transmission layers.
In some embodiments, the receiving port 1101 is further configured
to receive the information about the first number of maximum
transmission layers from the base station 603 when the first number
of transmission layers is larger than the second number of maximum
transmission layers. In some embodiments, the information about the
first number of maximum transmission layers is received from the
base station 603 via a radio resource control, referred to as RRC,
protocol. In some embodiments, the information about the first
number of maximum transmission layers is preconfigured in the user
equipment 605. In some embodiments, the selected user equipment
category and the first number of maximum transmission layers are
associated with release 8/9 of long term evolution, referred to as
LTE, and the second number of maximum transmission layers are
associated with release 10 of LTE. In some embodiments, the
selected user equipment category and the first number of maximum
transmission layers are associated with release 10 of LTE and the
second number of maximum transmission layers are associated with
release 8/9 of LTE.
[0165] The user equipment 605 comprises a determining unit 1103
configured to, based on information about the selected user
equipment category, determine a first number of maximum
transmission layers supported by the user equipment 605.
[0166] The user equipment 605 further comprises a communicating
unit 1105 configured to communicate with the base station 603
according to up to the first number of maximum transmission layers
and the selected user equipment category. In some embodiments, the
communicating with the base station 603 according to up to the
first number of maximum transmission layers and the selected user
equipment category is a downlink communication in a direction from
the base station 603 to the user equipment 605.
[0167] In some embodiments, the user equipment 605 comprises an
obtaining unit 1109 configured to obtain information about a state
of a radio channel 604 between the user equipment 605 and the base
station 603 and according to the first number of maximum
transmission layers.
[0168] In some embodiments, the user equipment 605 comprises a
transmitting port 1108 configured to transmit, to the base station
603, information about the at least two user equipment categories
and a number of maximum transmission layers for each user equipment
category. In some embodiments, the transmitting port 1108 is
further configured to transmit the channel state information to the
base station 603.
[0169] The present mechanism for communication between a user
equipment 605 and a base station 603 in a communication network 600
may be implemented through one or more processors, such as a
processing unit 1010 in the base station 603 depicted in FIG. 10
and a processing unit 1120 in the user equipment 605 depicted in
FIG. 11, together with computer program code for performing the
functions of the embodiments herein. The processor may be for
example a Digital Signal Processor (DSP), Application Specific
Integrated Circuit (ASIC) processor, Field-programmable gate array
(FPGA) processor or micro processor. The program code mentioned
above may also be provided as a computer program product, for
instance in the form of a data carrier carrying computer program
code for performing the embodiments herein when being loaded into
the user equipment 605 and/or the base station 603. One such
carrier may be in the form of a CD ROM disc. It is however feasible
with other data carriers such as a memory stick. The computer
program code may furthermore be provided as pure program code on a
server and downloaded to the user equipment 605 and/or the base
station 603 remotely.
[0170] FIG. 12 illustrates non-limiting functional block diagrams
of a base station 603 and a user equipment 605 for implementing the
technology described above including the capability signaling. The
base station 603 includes an overall base station controller 1201
coupled to one or more memories 1203 that performs soft buffering.
In relation to the user equipment 605, soft buffering may refer to
performing rate matching according to the total amount of soft
channel bits. In relation to the base station 603, soft buffering
may refer to performing rate matching according to the total amount
of soft channel bits. Radio Frequency (RF) circuitry 1205 is
coupled to multiple antennas 1208 for performing radio transmission
and reception for the base station. In FIG. 12, four antennas 1208
are shown as an example. The antennas 1208 in FIG. 12 corresponds
to the transmitting port 1003 and the receiving port 1009 in FIG.
10. The example of FIG. 12 shows that carrier aggregation is
supported. Multiple processors, corresponding to the determining
unit 1001, the processing unit 1010 and the communicating unit 1005
in FIG. 10, are shown for performing corresponding tasks including
HARQ processing 1210, UE category signaling processing 1212, and
MIMO layer processing 1215.
[0171] The user equipment 605 comprises similar processing and
memory blocks, and depending on its release, more or less
sophistication, bandwidth, and other capabilities. The user
equipment 605 comprises an overall user equipment controller 1220
coupled to one or more memories 1223 that performs soft buffering.
A RF circuitry 1225 is coupled to multiple antennas 1228 for
performing radio transmission and reception for the user equipment
605. In FIG. 12, two antennas 1228 are shown as an example. The
antennas 1228 in FIG. 12 corresponds to the transmitting port 1108
and the receiving port 1101 in FIG. 11. Multiple processors,
corresponding to the determining unit 1103, the processing unit
1120, the obtaining unit 1109 and the communicating unit 1105 in
FIG. 11, are shown for performing corresponding tasks including
HARQ processing 1230, UE category signaling processing 1232, and
MIMO layer processing 1235. The user equipment 605 further
comprises a user interface 1240 for enabling communication with a
user of the user equipment 605.
[0172] The above description sets forth specific details, such as
particular embodiments for purposes of explanation and not
limitation. But it will be appreciated by one skilled in the art
that other embodiments may be employed apart from these specific
details. In some instances, detailed descriptions of well known
methods, nodes, interfaces, circuits, and devices are omitted so as
not obscure the description with unnecessary detail. Those skilled
in the art will appreciate that the functions described may be
implemented in one or more nodes using hardware circuitry, e.g.,
analog and/or discrete logic gates interconnected to perform a
specialized function, ASICs, PLAs, etc. and/or using software
programs and data in conjunction with one or more digital
microprocessors or general purpose computers. Nodes that
communicate using the air interface also have suitable radio
communications circuitry. Moreover, the technology may additionally
be considered to be embodied entirely within any form of
computer-readable memory, such as solid-state memory, magnetic
disk, or optical disk containing an appropriate set of computer
instructions that would cause a processor to carry out the
techniques described herein.
[0173] Hardware implementation may include or encompass, without
limitation, digital signal processor (DSP) hardware, a reduced
instruction set processor, hardware, e.g., digital or analog,
circuitry including but not limited to application specific
integrated circuit(s) (ASIC) and/or field programmable gate
array(s) (FPGA(s)), and, where appropriate, state machines capable
of performing such functions.
[0174] In terms of computer implementation, a computer is generally
understood to comprise one or more processors or one or more
controllers, and the terms computer, processor, and controller may
be employed interchangeably. When provided by a computer,
processor, or controller, the functions may be provided by a single
dedicated computer or processor or controller, by a single shared
computer or processor or controller, or by a plurality of
individual computers or processors or controllers, some of which
may be shared or distributed. Moreover, the term "processor" or
"controller" also refers to other hardware capable of performing
such functions and/or executing software, such as the example
hardware recited above.
[0175] The description uses but is not limited to the non-limiting
release example introduced above.
[0176] Although the description above contains many specifics, they
may not be construed as limiting but as merely providing
illustrations of some presently preferred embodiments. The
technology fully encompasses other embodiments which may become
apparent to those skilled in the art. Reference to an element in
the singular is not intended to mean "one and only one" unless
explicitly so stated, but rather "one or more." All structural and
functional equivalents to the elements of the above-described
embodiments that are known to those of ordinary skill in the art
are expressly incorporated herein by reference and are intended to
be encompassed hereby. Moreover, it is not necessary for a device
or method to address each and every problem sought to be solved by
the described technology for it to be encompassed hereby.
* * * * *